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Title: Do entanglement islands exist for evaporating black holes in ordinary 4D gravity?
Plain: The island calculation assigns a region inside the black hole to the distant radiation. It is unclear whether this works when gravity acts everywhere with a massless graviton, as in our universe, instead of in model setups where the radiation escapes into a region without gravity.
Precise: Consider a 4D asymptotically flat Schwarzschild black hole evaporating to null infinity, with dynamical massless gravity everywhere and no non-gravitating bath. Does the prescription S(R) = min ext_I [A(boundary of I) c^3/(4 G hbar) + S_bulk(R u I)] with a nontrivial island I give a well-defined, gauge-invariant entropy for a radiation region R that follows the Page curve? Answer yes with a construction of R and I compatible with the gravitational Gauss law, or no with a proof that islands require a massive graviton or a non-gravitating region.
Settled by: A gauge-invariant definition of the radiation algebra at null infinity together with a computation of its entropy, or a no-go theorem from the gravitational constraints.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: contested
Status note: Arguments that islands require massive gravity (Geng and Karch 2020, extended 2025) and defenses of islands in massless gravity (2025) both stand as of 2026.
Posed since: 2020